An air-conditioning apparatus 1 for a railway vehicle (referred to below as an “air-conditioning apparatus 1”) that is mounted on a roof 51 of a railway vehicle 50, as illustrated in FIG. 11, is one of conventional air-conditioning apparatuses for a vehicle. During cooling operation, cold air 1a is sent to a vehicle interior 52 via air supply ducts 2 in communication with the air-conditioning apparatus 1. Circulating air 1b that has circulated through the vehicle interior 52 is sucked from return ducts 3 disposed between the vehicle 50 and the air-conditioning apparatus 1 into a return inlet 4 (see FIG. 12) and flows into the air-conditioning apparatus 1.
As illustrated in, for example, FIG. 12 and FIG. 13, the air-conditioning apparatus 1 is typically formed of an outdoor unit 9 and an indoor unit 5 and mounted on the roof 51 of the vehicle 50. The outdoor unit 9 and the indoor unit 5 are each equipped with air-conditioning equipment for ensuring the performance of air-conditioning. Air-conditioning equipment required for a refrigeration cycle, such as an outdoor fan 11, a condenser 12, which is an outdoor heat exchanger, a compressor 13, a pipe, and a wiring (not illustrated), is disposed in a housing 10 of the outdoor unit 9. Air-conditioning equipment, such as an indoor fan 7, an evaporator 8, which is an indoor heat exchanger, a return damper for adjusting the amount of air, a fresh damper, a controller, and a heater using an electric heat source, although these components are not illustrated, is disposed in a housing 6 of the indoor unit 5.
The flow of air inside the indoor unit 5 of the conventional air-conditioning apparatus 1 will be described. Inside the indoor unit 5, the indoor fan 7 is operated to suck air from the vehicle interior 52 into the indoor unit 5 via the return ducts 3, although this configuration is not illustrated. The sucked air passes through a dust collection filter, the evaporator 8, the indoor fan 7, and the heater in this order and subsequently returns to the vehicle interior 52 from an air supply duct opening. The circulating air 1b flows back into the indoor unit 5 again. Fresh air drawn from outdoor air into the indoor unit 5 flows to the vehicle interior 52 from the air supply duct opening as in the flow of the circulating air 1b. 
As well as the air-conditioning apparatus for a railway vehicle, the conventional air-conditioning apparatus 1 includes an air-conditioning apparatus for a motor vehicle. As illustrated in FIG. 14, a defroster of this air-conditioning apparatus for a motor vehicle causes air that has passed through a defroster air communication hole 60 to be sucked from an air suction port 62 of a box-shaped housing 61. The air passes through holes 63a of a U-shaped airflow direction plate 63 and blows as a jet of airflow 65 upward from the lower portion of a windshield 64 along a windshield surface, and hence condensation is removed. The size of the holes 63a gradually increases with an increase in the distance from the defroster air communication hole 60 in the longitudinal direction. A small amount of air is sucked from the hole 63a close to the air suction port 62, and a large amount of air is sucked from the large hole 63a on the opposite side. After the air blows from the U-shaped airflow direction plate 63, a pressure gradient in a space 77 partitioned by a partition plate 76 decreases, and condensation on the inner surface of the windshield 64 is removed from the entire surface. A noise of a vehicle engine coming from the defroster air communication hole 60 directly reaches the vehicle interior from the air suction port 62 of the box-shaped housing 61 via the holes 63a of the U-shaped airflow direction plate 63 (see, for example, Patent Literature 1).
The air-conditioning apparatus for a motor vehicle includes an air-conditioning apparatus for a motor vehicle that adjusts the amount of air using an airflow direction plate with a drive unit. As illustrated in FIG. 15, in this air-conditioning apparatus for a motor vehicle, the amount of cooling air and the amount of heating air are adjusted by rotating an airflow direction plate 70 for a motor vehicle using a servomotor to change the flow of air passing through a cooling bypass air passageway 73 extending from a fan 71 for a motor vehicle toward a cooling heat exchanger 72 and the flow of air passing through a heating air passageway 75 in a heater 74 for a motor vehicle (see, for example, Patent Literature 2).